Acoustic devices using an AlGaN piezoelectric region

Abstract

Provided is a method of forming an acoustic based device, including forming an AlGaN region having a first surface and a second surface. A first electrode is deposited on the first surface of the AlGaN region, and then a second electrode is deposited on a second surface of the AlGaN-region. In another aspect of the present application, the AlGaN region is formed by an epitaxial layer overgrowth process.

1. A method of forming an acoustical device comprising:
 providing a first substrate having a first surface and a second surface where the substrate is one of an r-plane sapphire, aluminum oxide (Al 2 O 3 ) or aluminum nitride (AlN); 
 growing a single crystal piezoelectric region having a first surface and a second surface, the single crystal piezoelectric region located on the first surface of the first substrate, wherein the first surface of the single crystal piezoelectric region and the first surface of the substrate are in direct contact; 
 depositing a first electrode layer on a second surface of the single crystal piezoelectric region; 
 performing a laser lift-off process including employing a radiation source to break a bond between the first surface of the first substrate and the first surface of the single crystal piezoelectric region to separate the first substrate and the single crystal piezoelectric region; 
 performing a laser trimming process with the radiation source; 
 smoothing the surface of the first surface of the single crystal piezoelectric region through polishing techniques in order to tune the first surface of the single crystal piezoelectric region to operate at a specific resonant frequency; and 
 depositing a second electrode layer on the first surface of the single crystal piezoelectric region. 
 
   
   
     2. The method according to  claim 1 , wherein the lift-off process includes,
 emitting, from the radiation source, a radiation beam through the first substrate to an attachment interface formed by the first substrate and the single crystal, wherein the first substrate is substantially transparent at the wavelength of the radiation beam, and the radiation beam generates sufficient absorbed energy at the interface to break the attachment. 
 
   
   
     3. The method according to  claim 2 , wherein the trimming process includes trimming the single crystal piezoelectric region to cause the single crystal piezoelectric region to resonate at a desired frequency. 
   
   
     4. The method according to  claim 2 , wherein following the step of depositing the first electrode, providing a gap forming arrangement on the same side as the first electrode. 
   
   
     5. The method according to  claim 4 , wherein prior to performing the liftoff process, bonding the gap forming arrangement to a second substrate. 
   
   
     6. The method according to  claim 1 , wherein the acoustical device is operational in at least one of a bulk resonant mode and a shear wave resonant mode. 
   
   
     7. An acoustical device that is operational in at least one of a bulk resonant mode and a shear wave resonant mode, comprising:
 an AlGaN region having a first surface and a second surface; 
 a first electrode deposited on the first surface of the AlGaN region; 
 a second electrode deposited on the second surface of the AlGaN region; 
 a first air or vacuum interface adjacent to at least a portion of the first surface of the AlGaN region and the first electrode; and 
 a second air or vacuum interface associated with at least a portion of the second surface of the AlGaN region and the second electrode, wherein the AlGaN region is a polycrystalline AlGaN region. 
 
   
   
     8. An acoustical device that is operational in at least one of a bulk resonant mode and a shear wave resonant mode, comprising:
 an AlGaN region having a first surface and a second surface; 
 a first electrode deposited on the first surface of the AlGaN region; 
 a second electrode deposited on the second surface of the AlGaN region; 
 a first air or vacuum interface adjacent to at least a portion of the first surface of the AlGaN region and the first electrode; and 
 a second air or vacuum interface associated with at least a portion of the second surface of the AlGaN region and the second electrode, wherein the AlGaN region is selected from a variety of AlGaN material types, having different values, from each other, of at least one of the Al and Ga components, and wherein In is used during growth and incorporated in the AlGaN region.